Prevalence of Toxocara Spp. eggs in Public Parks in Tehran City, Iran.

Background The objective of the present research was to determine the frequency of Toxocara spp. eggs in soil samples of public parks, in the city of Tehran, Iran. Methods A total of 600 soil samples were taken from 120 parks between Aprils to November, 2008. Soil samples were collected from 5 distinct sites in the parks. The samples were washed with saline solution and the collected sediment from each park were equally divided and examined by floatation and Petri dish methods for Toxocara eggs. Results Ten percent were contaminated with Toxocara spp. eggs. The number of observed Toxocara eggs in each microscopic field was varied from 1-3. No significant differences were observed between floatation and Petri dish methods. Conclusion Our public parks showed a high risk of toxocariasis and the need for preventive studies.

Introduction oxocara canis and T. cati are common intestinal parasites of dogs and cats. The soil contamination with eggs of these parasites is an important etiological factor in Toxocara infection of people. Human beings become infected by ingesting infective eggs (1)(2). Human infection with toxocariasis is mostly asymptomatic in the most individuals. However, the immune system unable to control larvae migration into liver, in these cases, otherwise involvement of central nervous system and/or eye can be occurring. Among children, the age groups most affected by severe clinical symptoms of larva migrant's syndrome are toddlers 1-3 years (3). The prevalence of Toxocara eggs infected soil is reported from 0.8 % in Costa Rica to 97.5% in Greece (6,7). There are few studies in Iran on the prevalence of Toxocara eggs in public parks. The purpose of this study was to point out the prevalence of contamination public parks with Toxocara spp. eggs in Tehran.

Materials and Methods
From April to November 2008, 120 parks were selected from 19 different zones of Tehran and soil samples were taken. Five soil samples, each 100g were collected (from north, south, west, east and central of each park). After pooling the samples of each park, a 500g sample was washed with saline solution into buckets through a set of 2 sieves having pore widths of 250µm and 150µm. The water collected in the bucket was left to sediment for 1-2 hours. The sediment from each park were equally divided and examined by floatation method with saturated salt solution (8) and Petri dish plate for Toxocara eggs. The sediment in petri dishes were diluted in saline and examined under stereomicroscope for the presence of Toxocara eggs.

Discussion
Toxocara spp. is the most common nematodes in dogs and cats. Human Toxocariasis develops by ingesting of embryonated eggs in contaminated soil. All individuals are susceptible to contamination; however, children play in the parks more than the adults.
In four serodiagnosis studies of toxocariasis in Iranian children have been shown as, 10 cases in Iran, 25.6% from Shiraz , south of Iran, 5.3% in west of Iran and 2.7% from northwest of Iran, respectively (5,(28)(29)(30).
In spite of the light contamination rate and low number of eggs found in this study it should be kept in mind that children always take a risk of visceral larva migrants while playing in contaminated playgrounds. For this reason, preventive measures should be implemented. These could include health education of the public health, good personal hygiene practice, control of stray dogs and cats.